1. Field of the Invention
This invention is related to power management in processors.
2. Description of the Related Art
The number of transistors that can be incorporated on a given semiconductor substrate to form an integrated circuit continues to increase. In parallel, the clock frequencies at which the integrated circuits are operated (the “operating frequencies”) also continue to increase. Although the supply voltage magnitude has decreased over time, the power consumption of the integrated circuits has been increasing. In cases in which the integrated circuits are used in devices with limited energy stores (e.g. mobile devices operating on a battery), the power consumption is a factor in how long the device can be used before the device must be recharged. Additionally, the heat generated through power consumption can be an issue in both mobile and non-mobile devices.
Devices that include processors to execute software can manage power consumption in the processors. Typically, a given processor can be stopped if there is no software currently in need of execution on that processor. Stopping a processor can include clock gating, in which the clock is stopped but the processor remains powered up and ready to execute instructions when the clock is restarted, and power gating in which the processor is powered down and will be powered up and reset before executing instructions.
Many devices include multiple processors, including mobile devices. Processors can also be significant power consumers, especially under certain workloads. Accordingly, there can be operating points (combinations of supply voltage magnitude and operating frequency) at which, if all the processors are actively executing, the device is at risk of exceeding the capacity of the power supply in the device. That is, the power supply is capable of sourcing a maximum amount of current. If all the processors are actively executing power-intensive workloads at some of the operating points, the resulting current draw can exceed the amount of current that the power supply can provide. Exceeding the capacity of the power supply may cause erroneous operation (e.g. the supply voltage magnitude may droop to a point at which the integrated circuit no longer operates properly at the operating frequency).